Method and apparatus for separating potatoes from stones and soil clods

ABSTRACT

This invention relates to a novel method for separating potatoes from stones and soil clods which comprises channeling a mixture thereof beneath a source of both visible and invisible light as well as infrared radiation covering that portion of the spectrum between approximately 0.2 Mu and 3.0 Mu , measuring the reflectance of each element of the mixture within the narrower band of approximately 0.6 Mu to 1.3 Mu as well as the band below the latter from about 1.4 to 2.0 Mu , formulating a ratio based thereon, comparing the ratios thus adduced for each element of the mixture and sorting the elements of the mixture into two groups having similar reflectance ratios. The invention also encompasses the novel apparatus for carrying out the aforesaid separation which comprises a first conveyor locatable at the discharge end of a conventional potato harvester adapted to receive a mixture of potatoes, stones and soil clods therefrom and channel same into a series of side-by-side parallel lines of individual elements; an emitter of both visible light and infrared radiation located above each line of elements in position to shine thereon one-at-a-time; differential detection means responsive to the light reflected from each element adapted to classify the latter into two categories based upon the ratio of their reflectivities within the selected radiant energy bands; and, sorting means connected to the detection means operative to separate each element of the mixture into one of two categories in accordance with the previously determined classification thereof.

O United States Patent [151 3,675,769 Story [451 July 1 1, 1972 54METHOD AND APPARATUS FOR 57 ABSTRACT SEPARATING POTATOES FROM Thisinvention relates to a novel method for separating STONES D SO C Opotatoes from stones and soil clods which comprises channeling a mixturethereof beneath a source of both visible and in- [72] Inventor AlbertFort Coums Colo visible light as well as infrared radiation coveringthat portion [73] Assignee: Colorado State University Research Founofthe spectrum between approximately 0.2;; and 3.0a, meadation, FortCollins, Colo. suring the reflectance of each element of the mixturewithin the narrower band of approximately 0.6 1. to 1.3;1. as well as[221 1971 the band below the latter from about 1.4 m 2.0 formulating[2i] Appl. No.: 112,322 a ratio based thereon, comparing the ratios thusadduced for each element of the mixture and sorting the elements of themixture into two groups having similar reflectance ratios. The [52] US.Cl ..209/73, 209/ l l l.5 invention'also encompasses the novel apparatusfor carrying [5 1] Int. Cl. B07c out the aforesaid separation whichcomprises a first conveyor [58] Field of Search ..209/1 1 1.5, 111.7,73, 74; i'ocatable at the discharge end of a conventional potato har-250/83 vester adapted to receive a mixture of potatoes, stones and soilciods therefrom and channel same into a series of side-by-side [56]References Cited parallel lines of individual elements; an emitter ofboth visible light and infrared radiation located above each line ofele- UNITED STATES PATENTS ments in position to shine thereonone-at-a-time; differential detection means responsive to the lightreflected from each gflman i element adapted to classify the latter intotwo categories 3435950 4 1969 l 5 based upon the ratio of theirreflectivities within the selected 79 l 971 x radiant energy bands; and,sorting means connected to the de- 3,594,5 arrett ..20 l 1.5 tecfionmeans p fi to Separate eaCh element f the Primary Examiner-Allen N.Knowles Attorney-Anderson, Spangler & Wymore ture into one of twocategories in accordance with the previously determined classificationthereof.

l0Claims,8DrawingFigures PATENTEDJUL 11 m2 3, 75,7 9

SHEET 1 0F 1 r I I I l II I 7\ 78 a6 INVENTOR ALBERT 6. STORY BY 77 7 "WATTORNEYS PATENTEDJUL 1 1 I972 SHEET H U? 4 INVENTQR",

METHOD AND APPARATUS FOR SEPARATING POTATOES FROM STONES AND SOIL CIJODSOperation of a conventional potato harvester in stony or cloddy soilresults in mixtures containing the latter undesirable elements movingonto the sorting apron along with the potatoes. By far the most widelyused method of removing the stones and soil clods from the mixture is byhand and several persons are customarily required to perform thisoperation. Even so, one pass is seldom sufficient to complete theseparation and, therefore, the mixture must be transferred from oneconveyor to another two or three times before all the stones and soilclods are removed. This repeated handling and abrasion of the delicatetubers hastens their decay if stored for pro-- longed periods of timeand often brings about a reduction in market grade for a significantproportion of the crop.

In an effort to overcome these problems and also bring about economiesin the harvesting operation, many automatic sorting techniques have beenattempted. Among these were tilted conveyors, elastic strips, flotationin both solutions and rising air streams, and rotating brushes. For themost part, the prior art mechanical separation techniques resulted ineither excessive damage to-the potatoes or incomplete sorting or both.

Another sorting technique has been investigated to a limited extentexperimentally that showed some promise of providing both completeseparation and minimal tuber damage, namely, the relative absorption andreflection of radiant energy between potatoes and foreign objects as ameans of differentiating therebetween. Differences in the abilityto'transmit X-rays proved to be a highly reliable method ofdifferentiating between the potatoes and stones or clods, however, theenergy source and detection circuit were both too expensive and toodangerous to be practical.

Other investigations attempted to differentiate between potatoes andboth stones and soil clods based upon the differences in absolutereflectances of an ordinary broad spectrum visible light source, but,they found that a complete separation was virtually unattainablepredicated upon this criteria. The main problem came from light-coloredrocks and similarly-colored dry clods which exhibited an absolutereflectance nearly the same as that of the potatoes.

By far the most encouraging results appear to be based upon a comparisonbetween the ratios of reflectances within a pair of selected band widthstaken from a broad spectrum that initially includes visible light andinvisible light in the ultraviolet-near-blue end of the spectrum. aswell as radiant energy in the infrared end thereof. In other words,rather than trying to predicate a sorting function upon differentiatingbetween the absolute reflectance of potatoes and soil clods or stonesover a broad band of radiant energy due to the known higher reflectanceof potatoes versus stones and soil clods in the red and infrared rangesthereof, it was found that a far more complete separation could beachieved by comparing the ratios of reflectance within the selected redto infrared-nearred band of approximately 0.6g. to 13 with the band oflonger wave length radiant energy immediately adjacent thereto thatextends from approximately 1.4 1. up to around 3.0" Since potatoesexhibit a high degree of reflectance in the red to infrared-near-redrange and a strong degree of absorption outside this band on both ends,one ratio can be derived which is readily compared and differentiatedfrom a second ratio based upon the reflectance of stones and clods whichexhibit a relatively more uniform spectral distribution of reflectivityover the entire range of radiant energy extending from 0.6;; all the wayup to 3.0g, although the absolute reflectance may be much higher thanpotatoes at wavelengths greater than about 1.4 1..

It has now been found in accordance with the teaching of the instantinvention that a reliable sorting method and apparatus for separatingpotatoes from stones and soil clods becomes practical based upon theaforementioned reflectance ratios. All elements of the mixture undergomechanical segregation preparatory to being channeled one-at-a-timebeneath a source of radiant energy that provides a discreet look at eachelement for sorting purposes. The energy source, while emitting light inboth the visible and invisible ends of the spectrum that includes theultraviolet-near-blue also emits considerable heat energy in theinfrared range yet remains very inexpensive and completely safe. Thereflected energy is collected and split into two separate beams, therelative intensities of which can be varied by an adjustablebeam-splitting mechanism. The reflected energy thus collected anddivided is then passed to separate yet identical photo cells, however,the character of the light reaching them is of a mutually-exclusive wavelength due to selective filtration. The magnitude of the band offiltered energy reaching one photo cell from a particular element iscombined with a like measure of a difi'erent band of filtered energyreaching the other detector and a ratio thereof is formed which is thenused to identify and differentiate between the various elements of theharvested mixture.

The resulting mechanism is fully automatic thus eliminating the need forany hand-sorting in an era where even common labor is both expensive andhard to find. Minimal handling of the potatoes is required thus assuringthat the crop will not be downgraded because of abuse during the sortingoperation. For the most part, the mechanical elements of the system aresimple, cheap and readily available even in farm communities. About theonly items that arent easily repaired in the field are the opticalsubassembly and the electromechanical subassembly; however, thesesubassemblies are quite rugged and, therefore, capable of withstandingconsiderable abuse. The electronic components are both simple andinexpensive. Even the optical components comprise little more thansilvered beam-splitting grids,simple double-convex collector lenses andinexpensive filters, none of which need even be of panicu larly highquality. In fact, both the optical and electronic subassemblies arewell-suited to modular treatment whereby an inoperative unit can bereplaced with a'serviceable one even in the field in a matter ofminutes.

It is, therefore, the principal object of the present invention toprovide a novel method and apparatus for sorting and separating potatoesfrom both stones and soil clods.

A second objective is the provision of a method of the typeaforementioned in which the sorting function is reliably performed bydiscriminating between the relative absorptive and reflectivecharacteristics of the elements of the mixture within selected bands ofvisible light and radiant energy in the infrared end of the spectrum.

Another objective of the invention herein disclosed and claimed is toprovide a potato separating apparatus which involves minimal handlingand abuse thereof while removing the stones and soil clods therefrom.

Still another objective is to provide a potato sorting and separatingdevice that is readily integrated with existing potato harvestingequipment.

An additional object is to provide a sorting method whereby the elementsof the heterogeneous mixture being sorted are segregated andindividually examined one-at-a-time in a plurality of parallel linesmoving simultaneously past a series of identical optical discriminators.

Further objects of the invention forming the subject matter hereof areto provide a potato separating apparatus that is fast, reliable, rugged,easy to repair and service, relatively inexpensive, compact, andsufficiently versatile to discriminate re liably between potatoes andboth stones and soil clods irrespective of the shape, specific gravity,rolling resistance, or other geological characteristics of the latter.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description of thedrawings that follows, and in which:

FIG. 1 is a perspective view looking down and to the left upon thesorting and separating apparatus of the present invention, it havingbeen shown located adjacent the discharge end of the soileseparatingrod-link conveyor that forms a part of a conventional potato harvester;however, the apparatus need not be located at that particular point inorder to operate;

FIG. 2 is a longitudinal section to an enlarged scale showing one of thesolenoid-actuated sorting gates and associated linkage that are used topass the potatoes on through the system while discharging the stones andsoil clods therefrom;

FIG. 3 is a rear fragmentary elevation to an enlarged scale showing onesection of the V-belt and pulley system that is used to channel theelements of the mixture into line relation preparatory to their passingbeneath the discriminators;

FIG. 4 is an end view to a somewhat enlarged scale showing the relativelocations of the energy source, the optical and electromechanicalsubassemblies of the differential discriminator as they are arrangedwithin the housing therefor;

FIG. 5 is a fragmentary section to a further enlarged scale showing thedetails of the optical subassembly and photo cell sensing elements ofphotoelectric detector housed therein;

FIG. 6 is a plan view of one of the silvered beam'splitting grids of theoptical subassembly; FIG. 7 is an edge view showing a pair of saidbeam-splitting grids superimposed one atop the other for relativeparallel adjustment; and,

FIG. 8 is a schematic view showing the electromechanical circuit used inassociation with the optical subassembly to trigger the sorting gate.

Referring next to the drawings for a detailed description of the presentinvention and, initially, to FIG. 1 for this purpose, reference numeral10 has been chosen to broadly designate the sorting and separatingapparatus in its entirety while numeral 12 denotes the discharge end ofthe rod-link conveyor apron that carries the mixture of potatoes, stonesand soil clods dug up by a conventional potato harvester of which saidapron forms an integral part. What will be denominated here as asegregating conveyor 14, for lack of a more definitive term, forms acontinuation of the harvester apron 12 and, as will be seen presently,functions to channel the individual elements of the harvested mixtureinto a plurality of tranversely spaced parallel lines moving, as before,in the direction of the arrows. Just before the elements of the mixtureleave the discharge end of the segregating conveyor, they passone-at-atime beneath a bank of differential discriminators 16 (FIG. 4)located within housing 18, the details of which will appear shortly. Forthe present it will suffice to point out that each of the severaldiscriminators is operative to differentiate between potatoes and stonesor soil clods passing therebeneath and to generate a triggering pulsewhenever a potato is detected.

As the aligned elements of the harvested mixture leave the discharge endof the segregating conveyor, they pass onto a similar bank ofindividually operated sorting gates 20 that bridge the gap between thelatter conveyor and another conveyor 22, which may be an integral partof a conventional potato harvester and which runs laterally in adirection normal to the previous flow. The sorting gates operateindependently of one another whenever a potato has been detected to rockforwardly to catch the potato and roll same down onto the lateralconveyor 22. The stones and soil clods, on the other hand, merely dropthrough the gap between the segregating conveyor 14 and the sortinggates in their unactuated position where they are redirected down ontothe ground under the machine.

Next, with reference to FIGS. 1 and 3, it will be seen that thesegregating conveyor 14 includes a horizontally disposed tranverselyextending drive shaft 24 located at the intake end thereof which mayeither be independently powered by a suitable prime mover (not shown)or, preferably, connected in synchronous driven relation to the adjacentshaft 26 (FIG. 1) of the harvester by an appropriate power transfermechanism such as the sprocket chain drive designated broadly by numeral28 in FIG. 1.

Shaft 24 mounts a series of V-belt pulleys 30 in side-by-side relationthat are all of the same diameter. Driven shaft 32 at the discharge endof the segregating conveyor, on the other hand, mounts three differentsizes of V-belt pulleys, 32L, 32M and 325. A set of six such pulleysarranged with a pair of the largest diameter pulleys 32L on the outside,a pair of the smallest ones 32S adjacent one another on the inside, andone of the medium sized pulleys 32M positioned between each large andsmall one as shown in FIG. 3, cooperate with one another and with theV-belts 34L, 34M and 34S connecting the latter to the pulleys 30longitudinally aligned therewith at the intake end of the segregatingconveyor to define a trough that becomes progressively deeper toward thedischarge end. Thus, as the mixture of potatoes, stones and soil clodsthat leaves the rod-link conveyor apron 12 of the harvester enters theintake end of the segregating conveyor, it immediately becomes subjectto the channeling action of the troughs so that by the time such mixturepasses beneath the discriminators 16, the three basically differenttypes of harvested elements found therein will have been rearranged intosingle file lines capable of being individually examined. By havingseveral of such lines in parallel side-by-side relation to one another,the entire output of the harvester can be accommodated with a pluralityof segregating, detecting, sorting and separating functions going onsimultaneously.

Referring next to FIG. 4 briefly, the differential discriminator 16 willbe seen to include longitudinally spaced banks of three differentsubassemblies mounted within a common housing 18. The first of these isthe energy source 36 which is connected through the bottom wall 38 ofthe housing and constit'utes, in the particular form shown, an ordinaryincandescent lamp bulb positioned to shine down on the elements of themixture passing single file therebeneath on the segregating conveyor.Such a lamp will radiate energy up into the ultraviolet nearblue end ofthe invisible light spectrum at about 0.2g, down through the visiblelight range and well down into the infrared at about 2.5 to 3.0g. Aswill appear presently, the sorting function can be carried out withnearly perfect results by sampling the reflectances within the somewhatnarrower bands of 0.6 l.3;r and 1.4 2.2g. thus leaving out the shorterwave lengths in the blue end of the spectrum as well as the ultraviolet,and also the longer wavelengths in the infrared end of the spectrum.

The next element in the differential discriminators located in housing18 is the optical subassembly 40 of the electro-optical detector thathas been indicated in a general way by numeral 42 and which will bedescribed in detail presently in connection with FIGS. 5, 6 and 7. Asrevealed in FIG. 4, one detector 42 is provided for each lamp bulb 36located immediately downstream thereof where the visible and radiantenergy reflected from the mixture of aligned elements passingtherebeneath will be reflected up into the optical subassembly 40. Thedetector 42, in addition to the optical subassembly 40, includes thephoto cell sensors 44A and 44B (FIGS. 5 and 8) of the electromechanicalsubassembly that has-been referred to generally by numeral 46 and whichboth sorts the potatoes from the foreign objects and triggers thesorting gates.

Now in FIG. 5, the optical subassembly will be seen to include adownwardly directed collector lens 48 housed in a tubular lens mount 50that receives the light reflected from the elements of the mixturemoving therebeneath and directs same onto a pair of sandwichedbeam-splitting grids 52 disposed at a 45 angle relative to said lightpath. Collector lens 48 is a simple double-convex lens and, aspreviously mentioned, it neednt even be of good optical quality asprecise resolution and definition are not nearly as important here asthey would be in an image-producing optical instrument. In fact, itwould seem that this is an ideal application for plastic lenses whichare both inexpensive and rugged while providing moderately good quality.

In FIGS. 6 and 7, it will be seen that the beam-splitting grids comprisemirrors having alternate transparent and silvered bands 54 and 56. Thus,as the reflected light impinges upon one of these grids, approximatelyhalf of it will pass on through while the other half will be reflectedoff at right angles.

In FIGS. 5 and 7, it will be noted that two grids are used inface-to-face sandwiched relation to one another. The housing 58 (FIG. 4)includes diagonally disposed channel 60 adapted to retain these gridsand permit one to be adjusted relative to the other. In the particularform illustrated, the lower or nearer of the two grids 52F is fixedwhile the other 52M is movable by means of adjustable stop 62 thatengages the latter along its lower edge. The purpose of the overlappinggrids is, of course, to permit one to vary the relative proportions ofthe light reaching each of the two photo cells 44A and 448.

Once again with reference to FIG. 5, it will be noted that as the twobeams leave the beam splitter 52, they each are passed through a pair ofdouble-convex lenses 64A and 64B disposed at right angles to one anotherthat further concentrate said beams and direct same on to theirrespective photo cells. Located directly in front of each photo cell inposition to intercept the beam is a filter 66A and 663. As is the casewith any filter, these pass light within a certain band of the spectrumand block out the remainder. In this instance, they are mutuallyexclusive in that one passes the band from about 0.6 to 1.3 1. while theother passes the one adjacent thereto of around 1.4;; to 2.2a. Filterscapable of discriminating within the selected band widths are readilyavailable commercially and at nominal cost. The detectors are leadsulfide photo conductive cells which exhibit a photosensitivityextending from about 0.5; well up into the infrared range to at least2.7;.t. They are also not subject to failure by aging or mechanicalvibration as are photomultiplier tubes which might be used in thevisible range.

Referring next to FIG. 8, the electromechanical subassembly 46 that bothdifferentiates between the potatoes and the stones and soil clods andtriggers the mechanism that actuates the sorting gates and sorts thelatter. We have the two photo cells 44A and 448 each connected in serieswith a current-limiting resistor 68 in a simple bridge circuit. A D.C.power supply 70 represented in the form of a pair of 12 V. batteriesconnected to provide a total potential of 24 V. from +12 V. to -l 2V.powers the circuit and the lamp 36.

When a stone or a soil clod passes beneath one of the discriminators 16,the amount of energy reflected therefrom in the 0.6 to 1.311. band isnot materially different than that reflected from the same object in the1.4 to 2.2;]. band. Accordingly, the photo cells 44A and 443 will bothbe rendered moderately conductive but to about the same degree so thatthe ratio of their conductances will be about 1:1. The resistors formingthe other side of the bridge may be so chosen that, under this conditionthe bridge output, when connected as illustrated across a conventionalelectronic operational amplifier 70, will cause a slightly negativepotential to be applied to the amplifier and nothing further happens.

If, on the other hand, a potato is detected by a discriminator, thephoto cell measuring the reflected energy in the 0.6 to 1.3g. band willbe rendered highly conductive to the strong reflections in this area,whereas, conversely, the other cell measuring the reflectance in the 1.4to 2.2 tband will be even less conductive than with stones and soilclods due to the strong tendency of potatoes to absorb energy in theinfrared end of the spectrum above 1.4g. Now, instead of a slightlynegative condition, the bridge sees a condition of stronglypositiveimbalances as the ratio of reflectances translated into photocell conductances causes the conductance of cell 44A to be considerablygreater than that of cell 448. Obviously this positive imbalance will beimpressed across the amplifier 70.

The bias thus impressed across amplifier 70 will be amplified severalhundred times depending upon the value of resistor 72 which may be ofthe variable type shown, but may also well be a fixed resistor. Theresulting amplified voltage is impressed across the base of atransistorized power circuit that has been broadly indicated by numeral74 and which functions to control the current to a solenoid which hasbeen similarly identified by numeral 76. In the particular embodimentillustrated, a time-delay 78 is interposed between the amplifier 70 andpower output 74. The diode in this time-delay serves to isolate theamplifier 70 from the output circuit 74 after the voltage at theamplifier output terminal drops below the voltage on the time-delaycapacitor. In this way, since the output impedance of the amplifier islow, the solenoid will actuate the sorting gate in a very fewmilliseconds after a potato is sensed, but gate retraction after thepotato passes beyond the field of view of the optical assembly may bedelayed as desired by varying the value of the timedelay resistor. Thisallows the potato sufficient time to roll onto the gate beforeretraction commences.

The electromechanical subassembly 46 described above is located as shownin FIG. 4 in the main discriminator housing 18 and is connected to boththe energy source 36 and the optical subassembly 40, the photo cells 44providing the connection with the latter subassembly. Ambient sunlightcould, if desired, be used as the energy source in place of lamp 36although the latter is preferred because it obviously can be dependedupon to shine when the sun is obscured by cloud cover and also becauseof its relatively constant energy output. It should, perhaps, also bementioned that the circuit of FIG. 8 is, by no means, the only one thatcould be used but rather it is intended as being merely representativeof one such circuit that has been found quite satisfactory. Forinstance, the circuit shown is designed to ignore the stones and soilclods and respond to only the potatoes. As such, the mechanism isideally suited for use under conditions where the undesirable elements,namely, the stones and clods, preponderate over the potatoes as is oftenthe case. Other foreign materials, such as dead vines and trash willthus also be sorted from the potatoes. On the other hand, shouldconditions exist where the harvest is relatively free of foreignobjects, it might be better to sense the stones and clods and actuatethe gates to remove same while ignoring the potatoes. This, of course,can easily be done and it would require only minor modifications in theapparatus and circuitry above described such as could easily beaccomplished by one of ordinary skill in the mechanical and electronicarts.

Finally, with reference to FIGS. 1 and 2, the mounting and operation ofthe sorting gates 20 will be set forth in detail. The normal orunactuated position of these sorting gates is that shown in full linesin FIG. 2 where each such gate is inclined downwardly toward lateralconveyor 22. Thus, each rock and soil clod that leaves the discharge endof the segregating conveyor 14 traveling rearwardly, will drop throughthe gap between the end of conveyor 14 and the upraised end of thesorting gate 20. At such time as a potato is detected, solenoid 76, willactuate to pull gate 20 down into its downwardly inclined position shownin broken lines in FIG. 2 where the potato will roll gently down ontolateral conveyor 22 and be transferred to a suitable potato-retrievalunit (not shown) moving alongside thereof.

In operation, the absence of a potato under the detector results in nogate motion, thus stones, clods, or other debris pass off the end of thechanneling conveyor and drop onto the ground or possibly a conveyorwhich would collect and dispose of the foreign materials. When a potatopasses under the detector, the gate is actuated immediately (within afew milliseconds) to the left closing the gap which previously existedbetween the end of the gate and the channeling conveyor. The potato thenpasses onto the gate which, after an electronically controlled timedelay to assure that the potato has sufficient time to be deposited onthe gate, then begins to retract to its original position carrying thepotato with it. If there is another potato immediately following, theelectronic actuating signal will be renewed and the retraction will notoccur, or if it has commenced, will stop and the gate is reactuatedimmediately. The purpose of this arrangement is to eliminate thenecessity for a potato to completely cross the gate before the gateretracts to its unactuated position thus allowing considerably fastercycling than would be possible if the potato was required to clear thegate before retraction.

A pair of longitudinally spaced frame members 78 and 80 extendtransversely across the unit between the discharge end of thesegregating conveyor and lateral conveyor 22. A U- shaped bracket 82pivotally mounts solenoid 76 between the frame elements and the core 84of said solenoid is pivotally attached to a corner at the base of atriangular member 86. The other corner at the base is pivotally attachedto one of the frame elements in fixed position by clevis 88 while asimilar clevis 96 attaches the third comer to the underside of the gate.Link 92 is similarly attached for pivotal movement between the otherframe element and the plate by clevises 90 and 94.

Upon actuation of the solenoid 76, its core 84 will retract and rock thetriangular plate 86 downwardly and to the right in FIG. 2 until itassumes the broken line position. As the forward pivot on the undersideof the gate 96 moves backward upon actuation of the solenoid, the rearpivot 90 is restrained by link 92 causing it to swing upwardly andbackwardly into a position causing the gate to be angled downwardly lesssharply than prior to actuation. As this occurs, the plate will rockbackwardly from its full line position into its broken line one.Solenoid 76 would be of the ordinary spring-return type which wouldinstantly resume its full line position the moment the current to itscoil was cut off.

As a matter of fact, the repeated energizations of the several solenoids76 in the unit would probably constitute an excessive drain on thelimited electrical power available in a field unit of this type;therefore, from a practical standpoint, the sorting gates 20 shouldprobably be actuated by either hydraulic or pneumatic servo-motorscontrolled by solenoidoperated valves of the well-known type. Hydraulicpower is usually available in farm machinery anyway and cutting down thepower requirements to that necessary for actuation of a solenoid valvewould seem to be a wise decision. Pneumatic power is even preferable tothe hydraulic because it is simpler, cheaper and faster acting, thelatter being especially important insofar as actuating the gates isconcerned. Here again, power is available from the internal combustionengine of the harvester or tractor to operate the compressor requiredfor pneumatic power. Thus, for the sake of simplicity, the solenoid 76has been shown as the direct actuator of the gate 20 when, in actuality,this would probably not be the case. The substitution of either ahydraulic or pneumatic solenoid-triggered gateactuating system would, ofcourse, be a simple matter for one skilled in these arts and call forthe exercise of no inventive faculties.

What is claimed is:

l. The apparatus for sorting and separating potatoes from stones andsoil clods which comprises:

segregating conveyor means locatable adjacent the potato flow path of apotato harvester in position to receive the harvested mixture ofpotatoes, stones and soil clods therefrom, said conveyor having theconveying surface thereof shaped to define a plurality of longitudinallyextending parallel troughs separated by upstanding ridges, said troughscooperating with one another and with the ridges therebetween to channelthe mixture into separate lines having the individual elements thereofmoving oneat-a-time toward the discharge end;

a transversely extending radiant energy source positioned adjacent thedischarge end of the segregating conveyor adapted to radiate anuninterrupted band of both visible and infrared energy down atop eachelement of the mixture in each line;

a sorting gate located at the discharge end of each trough in positionto intercept each element of the mixture issuing therefrom, said gatehaving two operative positions each adapted to deflect the elementsimpinging thereagainst along a different path;

optical means including a beam splitter positioned and adapted to gatherthe radiant energy reflected from each element in each line of themixture and divide same into two discreet beams;

first filter means positioned and adapted to intercept the radiantenergy in one of said beams and pass only that energy within the bandthat extends from the red down into the infrared-near-red end of thespectrum;

second filter means positioned and adapted to intercept the radiantenergy in the other of said beams and pass only that energy within thatband of the invisible spectrum that extends down from theinfrared-near-red into the longer discriminating means having a bridgewith a pair of photo cell sensors connected therein, one of said sensorsbeing positioned to intercept the filtered energy passing the firstfilter means and the second photo cell being positioned to intercept thefiltered energy passing the second filter means, said bridge circuitbeing operative when connected to a DC. power supply to compare therelative reflectances within the selected band widths of each elementsensed in terms of the relative conductances of the photo cells andgenerate a signal whenever the ratio of said conductances exceeds apredetermined value; and,

means connected to each sorting gate operative to shift the positionthereof in response to a signal generated within the discriminator meansassociated therewith.

2. The sorting and separating apparatus as set forth in claim 1 inwhich: the source of radiant energy emits within a band including atleast approximately 0.6 up to approximately 2.2;!"

3. The sorting and separating apparatus as set forth in claim 1 inwhich: the first filter means passes energy within the band ofapproximately 0.6;, up to approximately 1.3;1. and the second filtermeans passes energy between approximately 1.4;1. and approximately2.244..

4. The sorting and separating apparatus as set forth in claim 1 inwhich: the beam splitter comprises a pair of grids each having alternatetransparent and reflecting bands arranged in relatively adjustableface-to-face relation so that the ratio of reflected to transmittedenergy can be varied.

5. The sorting and separating apparatus as set forth in claim 1 inwhich: the segregating conveyor comprises a series of belts reaved inside-by-side parallel relation about longitudinally aligned pairs ofpulleys, at least those pulleys at the discharge end being graduated insize to define the troughs.

6. The sorting and separating apparatus as set forth in claim 1 inwhich: one position of the sorting gate is downwardly and forwardlyinclined so as to have an open gap between the leading edge of thelatter and the discharge end of the segregating conveyor sized to passstones and soil clods, and the second position thereof is downwardly andrearwardly inclined so as to form a continuation of said segregatingconveyor.

7. The sorting and separating apparatus as set forth in claim 5 inwhich: three pairs of pulleys of difierent diameters cooperate with sixpulleys of the same diameter to define a trough of steadily decreasingdepth toward the discharge end.

8. The sorting and separating apparatus as set forth in claim 6 inwhich: the signal generated by the discriminating means is operative toshift the sorting gate associated therewith from its first into itssecond position.

9. The method for sorting and separating potatoes from stones and soilclods which comprises: channeling the mixture of potatoes, stones andsoil clods into a plurality of parallel lines where the elements of saidmixture can be examined one at a time, passing each element of themixture beneath a source of radiant energy encompassing a band widththat includes at least the red end of the visible spectrum on downthrough a substantial portion of the infrared end of the invisiblespectrum, collecting the radiant energy reflected from each individualelement of the mixture and dividing same into two discreet beams,filtering one of said beams so as to include only red throughinfrared-near-red energy and the other of said beams so as to includethe remainder of the reflected infrared energy, sensing the energyreflected from each element within the selected bands and comparing therelative magnitudes thereof, and initiating a sorting functionpredicated upon the differences in relative reflectance magnitudeswithin said selected bands.

10. The method as set forth in claim 9 in which: the ele men'ts of themixture are passed beneath a radiant energy source encompassing at leastapproximately 0.6a up to approximately 2.2p., and the first beam isfiltered to pass energy between approximately 0.6g. and approximately1.3 u.

1. The apparatus for sorting and separating potatoes from stones andsoil clods which comprises: segregating conveyor means locatableadjacent the potato flow path of a potato harvester in position toreceive the harvested mixture of potatoes, stones and soil clodstherefrom, said conveyor having the conveying surface thereof shaped todefine a plurality of longitudinally extending parallel troughsseparated by upstanding ridges, said troughs cooperating with oneanother and with the ridges therebetween to channel the mixture intoseparate lines having the individual elements thereof movingone-at-a-time toward the discharge end; a transversely extending radiantenergy source positioned adjacent the discharge end of the segregatingconveyor adapted to radiate an uninterrupted band of both visible andinfrared energy down atop each element of the mixture in each line; asorting gate located at the discharge end of each trough in position tointercept each element of the mixture issuing therefrom, said gatehaving two operative positions each adapted to deflect the elementsimpinging thereagainst along a different path; optical means including abeam splitter positioned and adapted to gather the radiant energyreflected from each element in each line of the mixture and divide sameinto two discreet beams; first filter meanS positioned and adapted tointercept the radiant energy in one of said beams and pass only thatenergy within the band that extends from the red down into theinfrared-near-red end of the spectrum; second filter means positionedand adapted to intercept the radiant energy in the other of said beamsand pass only that energy within that band of the invisible spectrumthat extends down from the infrared-near-red into the longer wave lengthinfrared; discriminating means having a bridge with a pair of photo cellsensors connected therein, one of said sensors being positioned tointercept the filtered energy passing the first filter means and thesecond photo cell being positioned to intercept the filtered energypassing the second filter means, said bridge circuit being operativewhen connected to a D.C. power supply to compare the relativereflectances within the selected band widths of each element sensed interms of the relative conductances of the photo cells and generate asignal whenever the ratio of said conductances exceeds a predeterminedvalue; and, means connected to each sorting gate operative to shift theposition thereof in response to a signal generated within thediscriminator means associated therewith.
 2. The sorting and separatingapparatus as set forth in claim 1 in which: the source of radiant energyemits within a band including at least approximately 0.6 Mu up toapproximately 2.2 Mu .
 3. The sorting and separating apparatus as setforth in claim 1 in which: the first filter means passes energy withinthe band of approximately 0.6 Mu up to approximately 1.3 Mu and thesecond filter means passes energy between approximately 1.4 Mu andapproximately 2.2 Mu .
 4. The sorting and separating apparatus as setforth in claim 1 in which: the beam splitter comprises a pair of gridseach having alternate transparent and reflecting bands arranged inrelatively adjustable face-to-face relation so that the ratio ofreflected to transmitted energy can be varied.
 5. The sorting andseparating apparatus as set forth in claim 1 in which: the segregatingconveyor comprises a series of belts reaved in side-by-side parallelrelation about longitudinally aligned pairs of pulleys, at least thosepulleys at the discharge end being graduated in size to define thetroughs.
 6. The sorting and separating apparatus as set forth in claim 1in which: one position of the sorting gate is downwardly and forwardlyinclined so as to have an open gap between the leading edge of thelatter and the discharge end of the segregating conveyor sized to passstones and soil clods, and the second position thereof is downwardly andrearwardly inclined so as to form a continuation of said segregatingconveyor.
 7. The sorting and separating apparatus as set forth in claim5 in which: three pairs of pulleys of different diameters cooperate withsix pulleys of the same diameter to define a trough of steadilydecreasing depth toward the discharge end.
 8. The sorting and separatingapparatus as set forth in claim 6 in which: the signal generated by thediscriminating means is operative to shift the sorting gate associatedtherewith from its first into its second position.
 9. The method forsorting and separating potatoes from stones and soil clods whichcomprises: channeling the mixture of potatoes, stones and soil clodsinto a plurality of parallel lines where the elements of said mixturecan be examined one at a time, passing each element of the mixturebeneath a source of radiant energy encompassing a band width thatincludes at least the red end of the visible spectrum on down through asubstantial portion of the infrared end of the invisible spectrum,collecting the radiant energy reflected from each individual element ofthe mixture and dividing same into two discreet beams, filtering one ofsaid beams so as to include only red through infrared-near-red energyand the other of said beams so as to include the remainder of thereflected infrared energy, sensing the energy reflected from eachelement within the selected bands and comparing the relative magnitudesthereof, and initiating a sorting function predicated upon thedifferences in relative reflectance magnitudes within said selectedbands.
 10. The method as set forth in claim 9 in which: the elements ofthe mixture are passed beneath a radiant energy source encompassing atleast approximately 0.6 Mu up to approximately 2.2 Mu , and the firstbeam is filtered to pass energy between approximately 0.6 Mu andapproximately 1.3 Mu .